ITwebs I understand if you don't want to mess up what works, but if you encounter another iPhone that's unusable after an OS upgrade (or similar scenario) I'd be very interested in what a DFU restore does for it.
My understanding is that a DFU restore is a more low level initialization of the device, and is more "atomic", as in, the end result should always be the same assuming you're restoring the same IPSW no matter how many times you consecutively run the operation (SHSH blobs notwithstanding).